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- #
- # $Id: Encode.pm,v 2.23 2007/05/29 18:15:32 dankogai Exp dankogai $
- #
- package Encode;
- use strict;
- use warnings;
- our $VERSION = sprintf "%d.%02d", q$Revision: 2.23 $ =~ /(\d+)/g;
- sub DEBUG () { 0 }
- use XSLoader ();
- XSLoader::load( __PACKAGE__, $VERSION );
-
- require Exporter;
- use base qw/Exporter/;
-
- # Public, encouraged API is exported by default
-
- our @EXPORT = qw(
- decode decode_utf8 encode encode_utf8 str2bytes bytes2str
- encodings find_encoding clone_encoding
- );
- our @FB_FLAGS = qw(
- DIE_ON_ERR WARN_ON_ERR RETURN_ON_ERR LEAVE_SRC
- PERLQQ HTMLCREF XMLCREF STOP_AT_PARTIAL
- );
- our @FB_CONSTS = qw(
- FB_DEFAULT FB_CROAK FB_QUIET FB_WARN
- FB_PERLQQ FB_HTMLCREF FB_XMLCREF
- );
- our @EXPORT_OK = (
- qw(
- _utf8_off _utf8_on define_encoding from_to is_16bit is_8bit
- is_utf8 perlio_ok resolve_alias utf8_downgrade utf8_upgrade
- ),
- @FB_FLAGS, @FB_CONSTS,
- );
-
- our %EXPORT_TAGS = (
- all => [ @EXPORT, @EXPORT_OK ],
- fallbacks => [@FB_CONSTS],
- fallback_all => [ @FB_CONSTS, @FB_FLAGS ],
- );
-
- # Documentation moved after __END__ for speed - NI-S
-
- our $ON_EBCDIC = ( ord("A") == 193 );
-
- use Encode::Alias;
-
- # Make a %Encoding package variable to allow a certain amount of cheating
- our %Encoding;
- our %ExtModule;
- require Encode::Config;
- eval { require Encode::ConfigLocal };
-
- sub encodings {
- my $class = shift;
- my %enc;
- if ( @_ and $_[0] eq ":all" ) {
- %enc = ( %Encoding, %ExtModule );
- }
- else {
- %enc = %Encoding;
- for my $mod ( map { m/::/o ? $_ : "Encode::$_" } @_ ) {
- DEBUG and warn $mod;
- for my $enc ( keys %ExtModule ) {
- $ExtModule{$enc} eq $mod and $enc{$enc} = $mod;
- }
- }
- }
- return sort { lc $a cmp lc $b }
- grep { !/^(?:Internal|Unicode|Guess)$/o } keys %enc;
- }
-
- sub perlio_ok {
- my $obj = ref( $_[0] ) ? $_[0] : find_encoding( $_[0] );
- $obj->can("perlio_ok") and return $obj->perlio_ok();
- return 0; # safety net
- }
-
- sub define_encoding {
- my $obj = shift;
- my $name = shift;
- $Encoding{$name} = $obj;
- my $lc = lc($name);
- define_alias( $lc => $obj ) unless $lc eq $name;
- while (@_) {
- my $alias = shift;
- define_alias( $alias, $obj );
- }
- return $obj;
- }
-
- sub getEncoding {
- my ( $class, $name, $skip_external ) = @_;
-
- ref($name) && $name->can('renew') and return $name;
- exists $Encoding{$name} and return $Encoding{$name};
- my $lc = lc $name;
- exists $Encoding{$lc} and return $Encoding{$lc};
-
- my $oc = $class->find_alias($name);
- defined($oc) and return $oc;
- $lc ne $name and $oc = $class->find_alias($lc);
- defined($oc) and return $oc;
-
- unless ($skip_external) {
- if ( my $mod = $ExtModule{$name} || $ExtModule{$lc} ) {
- $mod =~ s,::,/,g;
- $mod .= '.pm';
- eval { require $mod; };
- exists $Encoding{$name} and return $Encoding{$name};
- }
- }
- return;
- }
-
- sub find_encoding($;$) {
- my ( $name, $skip_external ) = @_;
- return __PACKAGE__->getEncoding( $name, $skip_external );
- }
-
- sub resolve_alias($) {
- my $obj = find_encoding(shift);
- defined $obj and return $obj->name;
- return;
- }
-
- sub clone_encoding($) {
- my $obj = find_encoding(shift);
- ref $obj or return;
- eval { require Storable };
- $@ and return;
- return Storable::dclone($obj);
- }
-
- sub encode($$;$) {
- my ( $name, $string, $check ) = @_;
- return undef unless defined $string;
- $string .= '' if ref $string; # stringify;
- $check ||= 0;
- my $enc = find_encoding($name);
- unless ( defined $enc ) {
- require Carp;
- Carp::croak("Unknown encoding '$name'");
- }
- my $octets = $enc->encode( $string, $check );
- $_[1] = $string if $check and !ref $check and !( $check & LEAVE_SRC() );
- return $octets;
- }
- *str2bytes = \&encode;
-
- sub decode($$;$) {
- my ( $name, $octets, $check ) = @_;
- return undef unless defined $octets;
- $octets .= '' if ref $octets;
- $check ||= 0;
- my $enc = find_encoding($name);
- unless ( defined $enc ) {
- require Carp;
- Carp::croak("Unknown encoding '$name'");
- }
- my $string = $enc->decode( $octets, $check );
- $_[1] = $octets if $check and !ref $check and !( $check & LEAVE_SRC() );
- return $string;
- }
- *bytes2str = \&decode;
-
- sub from_to($$$;$) {
- my ( $string, $from, $to, $check ) = @_;
- return undef unless defined $string;
- $check ||= 0;
- my $f = find_encoding($from);
- unless ( defined $f ) {
- require Carp;
- Carp::croak("Unknown encoding '$from'");
- }
- my $t = find_encoding($to);
- unless ( defined $t ) {
- require Carp;
- Carp::croak("Unknown encoding '$to'");
- }
- my $uni = $f->decode($string);
- $_[0] = $string = $t->encode( $uni, $check );
- return undef if ( $check && length($uni) );
- return defined( $_[0] ) ? length($string) : undef;
- }
-
- sub encode_utf8($) {
- my ($str) = @_;
- utf8::encode($str);
- return $str;
- }
-
- sub decode_utf8($;$) {
- my ( $str, $check ) = @_;
- return $str if is_utf8($str);
- if ($check) {
- return decode( "utf8", $str, $check );
- }
- else {
- return decode( "utf8", $str );
- return $str;
- }
- }
-
- predefine_encodings(1);
-
- #
- # This is to restore %Encoding if really needed;
- #
-
- sub predefine_encodings {
- require Encode::Encoding;
- no warnings 'redefine';
- my $use_xs = shift;
- if ($ON_EBCDIC) {
-
- # was in Encode::UTF_EBCDIC
- package Encode::UTF_EBCDIC;
- push @Encode::UTF_EBCDIC::ISA, 'Encode::Encoding';
- *decode = sub {
- my ( $obj, $str, $chk ) = @_;
- my $res = '';
- for ( my $i = 0 ; $i < length($str) ; $i++ ) {
- $res .=
- chr(
- utf8::unicode_to_native( ord( substr( $str, $i, 1 ) ) )
- );
- }
- $_[1] = '' if $chk;
- return $res;
- };
- *encode = sub {
- my ( $obj, $str, $chk ) = @_;
- my $res = '';
- for ( my $i = 0 ; $i < length($str) ; $i++ ) {
- $res .=
- chr(
- utf8::native_to_unicode( ord( substr( $str, $i, 1 ) ) )
- );
- }
- $_[1] = '' if $chk;
- return $res;
- };
- $Encode::Encoding{Unicode} =
- bless { Name => "UTF_EBCDIC" } => "Encode::UTF_EBCDIC";
- }
- else {
-
- package Encode::Internal;
- push @Encode::Internal::ISA, 'Encode::Encoding';
- *decode = sub {
- my ( $obj, $str, $chk ) = @_;
- utf8::upgrade($str);
- $_[1] = '' if $chk;
- return $str;
- };
- *encode = \&decode;
- $Encode::Encoding{Unicode} =
- bless { Name => "Internal" } => "Encode::Internal";
- }
-
- {
-
- # was in Encode::utf8
- package Encode::utf8;
- push @Encode::utf8::ISA, 'Encode::Encoding';
-
- #
- if ($use_xs) {
- Encode::DEBUG and warn __PACKAGE__, " XS on";
- *decode = \&decode_xs;
- *encode = \&encode_xs;
- }
- else {
- Encode::DEBUG and warn __PACKAGE__, " XS off";
- *decode = sub {
- my ( $obj, $octets, $chk ) = @_;
- my $str = Encode::decode_utf8($octets);
- if ( defined $str ) {
- $_[1] = '' if $chk;
- return $str;
- }
- return undef;
- };
- *encode = sub {
- my ( $obj, $string, $chk ) = @_;
- my $octets = Encode::encode_utf8($string);
- $_[1] = '' if $chk;
- return $octets;
- };
- }
- *cat_decode = sub { # ($obj, $dst, $src, $pos, $trm, $chk)
- # currently ignores $chk
- my ( $obj, undef, undef, $pos, $trm ) = @_;
- my ( $rdst, $rsrc, $rpos ) = \@_[ 1, 2, 3 ];
- use bytes;
- if ( ( my $npos = index( $$rsrc, $trm, $pos ) ) >= 0 ) {
- $$rdst .=
- substr( $$rsrc, $pos, $npos - $pos + length($trm) );
- $$rpos = $npos + length($trm);
- return 1;
- }
- $$rdst .= substr( $$rsrc, $pos );
- $$rpos = length($$rsrc);
- return '';
- };
- $Encode::Encoding{utf8} =
- bless { Name => "utf8" } => "Encode::utf8";
- $Encode::Encoding{"utf-8-strict"} =
- bless { Name => "utf-8-strict", strict_utf8 => 1 } =>
- "Encode::utf8";
- }
- }
-
- 1;
-
- __END__
-
- =head1 NAME
-
- Encode - character encodings
-
- =head1 SYNOPSIS
-
- use Encode;
-
- =head2 Table of Contents
-
- Encode consists of a collection of modules whose details are too big
- to fit in one document. This POD itself explains the top-level APIs
- and general topics at a glance. For other topics and more details,
- see the PODs below:
-
- Name Description
- --------------------------------------------------------
- Encode::Alias Alias definitions to encodings
- Encode::Encoding Encode Implementation Base Class
- Encode::Supported List of Supported Encodings
- Encode::CN Simplified Chinese Encodings
- Encode::JP Japanese Encodings
- Encode::KR Korean Encodings
- Encode::TW Traditional Chinese Encodings
- --------------------------------------------------------
-
- =head1 DESCRIPTION
-
- The C<Encode> module provides the interfaces between Perl's strings
- and the rest of the system. Perl strings are sequences of
- B<characters>.
-
- The repertoire of characters that Perl can represent is at least that
- defined by the Unicode Consortium. On most platforms the ordinal
- values of the characters (as returned by C<ord(ch)>) is the "Unicode
- codepoint" for the character (the exceptions are those platforms where
- the legacy encoding is some variant of EBCDIC rather than a super-set
- of ASCII - see L<perlebcdic>).
-
- Traditionally, computer data has been moved around in 8-bit chunks
- often called "bytes". These chunks are also known as "octets" in
- networking standards. Perl is widely used to manipulate data of many
- types - not only strings of characters representing human or computer
- languages but also "binary" data being the machine's representation of
- numbers, pixels in an image - or just about anything.
-
- When Perl is processing "binary data", the programmer wants Perl to
- process "sequences of bytes". This is not a problem for Perl - as a
- byte has 256 possible values, it easily fits in Perl's much larger
- "logical character".
-
- =head2 TERMINOLOGY
-
- =over 2
-
- =item *
-
- I<character>: a character in the range 0..(2**32-1) (or more).
- (What Perl's strings are made of.)
-
- =item *
-
- I<byte>: a character in the range 0..255
- (A special case of a Perl character.)
-
- =item *
-
- I<octet>: 8 bits of data, with ordinal values 0..255
- (Term for bytes passed to or from a non-Perl context, e.g. a disk file.)
-
- =back
-
- =head1 PERL ENCODING API
-
- =over 2
-
- =item $octets = encode(ENCODING, $string [, CHECK])
-
- Encodes a string from Perl's internal form into I<ENCODING> and returns
- a sequence of octets. ENCODING can be either a canonical name or
- an alias. For encoding names and aliases, see L</"Defining Aliases">.
- For CHECK, see L</"Handling Malformed Data">.
-
- For example, to convert a string from Perl's internal format to
- iso-8859-1 (also known as Latin1),
-
- $octets = encode("iso-8859-1", $string);
-
- B<CAVEAT>: When you run C<$octets = encode("utf8", $string)>, then
- $octets B<may not be equal to> $string. Though they both contain the
- same data, the UTF8 flag for $octets is B<always> off. When you
- encode anything, UTF8 flag of the result is always off, even when it
- contains completely valid utf8 string. See L</"The UTF8 flag"> below.
-
- If the $string is C<undef> then C<undef> is returned.
-
- =item $string = decode(ENCODING, $octets [, CHECK])
-
- Decodes a sequence of octets assumed to be in I<ENCODING> into Perl's
- internal form and returns the resulting string. As in encode(),
- ENCODING can be either a canonical name or an alias. For encoding names
- and aliases, see L</"Defining Aliases">. For CHECK, see
- L</"Handling Malformed Data">.
-
- For example, to convert ISO-8859-1 data to a string in Perl's internal format:
-
- $string = decode("iso-8859-1", $octets);
-
- B<CAVEAT>: When you run C<$string = decode("utf8", $octets)>, then $string
- B<may not be equal to> $octets. Though they both contain the same data,
- the UTF8 flag for $string is on unless $octets entirely consists of
- ASCII data (or EBCDIC on EBCDIC machines). See L</"The UTF8 flag">
- below.
-
- If the $string is C<undef> then C<undef> is returned.
-
- =item [$obj =] find_encoding(ENCODING)
-
- Returns the I<encoding object> corresponding to ENCODING. Returns
- undef if no matching ENCODING is find.
-
- This object is what actually does the actual (en|de)coding.
-
- $utf8 = decode($name, $bytes);
-
- is in fact
-
- $utf8 = do{
- $obj = find_encoding($name);
- croak qq(encoding "$name" not found) unless ref $obj;
- $obj->decode($bytes)
- };
-
- with more error checking.
-
- Therefore you can save time by reusing this object as follows;
-
- my $enc = find_encoding("iso-8859-1");
- while(<>){
- my $utf8 = $enc->decode($_);
- # and do someting with $utf8;
- }
-
- Besides C<< ->decode >> and C<< ->encode >>, other methods are
- available as well. For instance, C<< -> name >> returns the canonical
- name of the encoding object.
-
- find_encoding("latin1")->name; # iso-8859-1
-
- See L<Encode::Encoding> for details.
-
- =item [$length =] from_to($octets, FROM_ENC, TO_ENC [, CHECK])
-
- Converts B<in-place> data between two encodings. The data in $octets
- must be encoded as octets and not as characters in Perl's internal
- format. For example, to convert ISO-8859-1 data to Microsoft's CP1250
- encoding:
-
- from_to($octets, "iso-8859-1", "cp1250");
-
- and to convert it back:
-
- from_to($octets, "cp1250", "iso-8859-1");
-
- Note that because the conversion happens in place, the data to be
- converted cannot be a string constant; it must be a scalar variable.
-
- from_to() returns the length of the converted string in octets on
- success, I<undef> on error.
-
- B<CAVEAT>: The following operations look the same but are not quite so;
-
- from_to($data, "iso-8859-1", "utf8"); #1
- $data = decode("iso-8859-1", $data); #2
-
- Both #1 and #2 make $data consist of a completely valid UTF-8 string
- but only #2 turns UTF8 flag on. #1 is equivalent to
-
- $data = encode("utf8", decode("iso-8859-1", $data));
-
- See L</"The UTF8 flag"> below.
-
- Also note that
-
- from_to($octets, $from, $to, $check);
-
- is equivalent to
-
- $octets = encode($to, decode($from, $octets), $check);
-
- Yes, it does not respect the $check during decoding. It is
- deliberately done that way. If you need minute control, C<decode>
- then C<encode> as follows;
-
- $octets = encode($to, decode($from, $octets, $check_from), $check_to);
-
- =item $octets = encode_utf8($string);
-
- Equivalent to C<$octets = encode("utf8", $string);> The characters
- that comprise $string are encoded in Perl's internal format and the
- result is returned as a sequence of octets. All possible
- characters have a UTF-8 representation so this function cannot fail.
-
-
- =item $string = decode_utf8($octets [, CHECK]);
-
- equivalent to C<$string = decode("utf8", $octets [, CHECK])>.
- The sequence of octets represented by
- $octets is decoded from UTF-8 into a sequence of logical
- characters. Not all sequences of octets form valid UTF-8 encodings, so
- it is possible for this call to fail. For CHECK, see
- L</"Handling Malformed Data">.
-
- =back
-
- =head2 Listing available encodings
-
- use Encode;
- @list = Encode->encodings();
-
- Returns a list of the canonical names of the available encodings that
- are loaded. To get a list of all available encodings including the
- ones that are not loaded yet, say
-
- @all_encodings = Encode->encodings(":all");
-
- Or you can give the name of a specific module.
-
- @with_jp = Encode->encodings("Encode::JP");
-
- When "::" is not in the name, "Encode::" is assumed.
-
- @ebcdic = Encode->encodings("EBCDIC");
-
- To find out in detail which encodings are supported by this package,
- see L<Encode::Supported>.
-
- =head2 Defining Aliases
-
- To add a new alias to a given encoding, use:
-
- use Encode;
- use Encode::Alias;
- define_alias(newName => ENCODING);
-
- After that, newName can be used as an alias for ENCODING.
- ENCODING may be either the name of an encoding or an
- I<encoding object>
-
- But before you do so, make sure the alias is nonexistent with
- C<resolve_alias()>, which returns the canonical name thereof.
- i.e.
-
- Encode::resolve_alias("latin1") eq "iso-8859-1" # true
- Encode::resolve_alias("iso-8859-12") # false; nonexistent
- Encode::resolve_alias($name) eq $name # true if $name is canonical
-
- resolve_alias() does not need C<use Encode::Alias>; it can be
- exported via C<use Encode qw(resolve_alias)>.
-
- See L<Encode::Alias> for details.
-
- =head2 Finding IANA Character Set Registry names
-
- The canonical name of a given encoding does not necessarily agree with
- IANA IANA Character Set Registry, commonly seen as C<< Content-Type:
- text/plain; charset=I<whatever> >>. For most cases canonical names
- work but sometimes it does not (notably 'utf-8-strict').
-
- Therefore as of Encode version 2.21, a new method C<mime_name()> is added.
-
- use Encode;
- my $enc = find_encoding('UTF-8');
- warn $enc->name; # utf-8-strict
- warn $enc->mime_name; # UTF-8
-
- See also: L<Encode::Encoding>
-
- =head1 Encoding via PerlIO
-
- If your perl supports I<PerlIO> (which is the default), you can use a
- PerlIO layer to decode and encode directly via a filehandle. The
- following two examples are totally identical in their functionality.
-
- # via PerlIO
- open my $in, "<:encoding(shiftjis)", $infile or die;
- open my $out, ">:encoding(euc-jp)", $outfile or die;
- while(<$in>){ print $out $_; }
-
- # via from_to
- open my $in, "<", $infile or die;
- open my $out, ">", $outfile or die;
- while(<$in>){
- from_to($_, "shiftjis", "euc-jp", 1);
- print $out $_;
- }
-
- Unfortunately, it may be that encodings are PerlIO-savvy. You can check
- if your encoding is supported by PerlIO by calling the C<perlio_ok>
- method.
-
- Encode::perlio_ok("hz"); # False
- find_encoding("euc-cn")->perlio_ok; # True where PerlIO is available
-
- use Encode qw(perlio_ok); # exported upon request
- perlio_ok("euc-jp")
-
- Fortunately, all encodings that come with Encode core are PerlIO-savvy
- except for hz and ISO-2022-kr. For gory details, see
- L<Encode::Encoding> and L<Encode::PerlIO>.
-
- =head1 Handling Malformed Data
-
- The optional I<CHECK> argument tells Encode what to do when it
- encounters malformed data. Without CHECK, Encode::FB_DEFAULT ( == 0 )
- is assumed.
-
- As of version 2.12 Encode supports coderef values for CHECK. See below.
-
- =over 2
-
- =item B<NOTE:> Not all encoding support this feature
-
- Some encodings ignore I<CHECK> argument. For example,
- L<Encode::Unicode> ignores I<CHECK> and it always croaks on error.
-
- =back
-
- Now here is the list of I<CHECK> values available
-
- =over 2
-
- =item I<CHECK> = Encode::FB_DEFAULT ( == 0)
-
- If I<CHECK> is 0, (en|de)code will put a I<substitution character> in
- place of a malformed character. When you encode, E<lt>subcharE<gt>
- will be used. When you decode the code point C<0xFFFD> is used. If
- the data is supposed to be UTF-8, an optional lexical warning
- (category utf8) is given.
-
- =item I<CHECK> = Encode::FB_CROAK ( == 1)
-
- If I<CHECK> is 1, methods will die on error immediately with an error
- message. Therefore, when I<CHECK> is set to 1, you should trap the
- error with eval{} unless you really want to let it die.
-
- =item I<CHECK> = Encode::FB_QUIET
-
- If I<CHECK> is set to Encode::FB_QUIET, (en|de)code will immediately
- return the portion of the data that has been processed so far when an
- error occurs. The data argument will be overwritten with everything
- after that point (that is, the unprocessed part of data). This is
- handy when you have to call decode repeatedly in the case where your
- source data may contain partial multi-byte character sequences,
- (i.e. you are reading with a fixed-width buffer). Here is a sample
- code that does exactly this:
-
- my $buffer = ''; my $string = '';
- while(read $fh, $buffer, 256, length($buffer)){
- $string .= decode($encoding, $buffer, Encode::FB_QUIET);
- # $buffer now contains the unprocessed partial character
- }
-
- =item I<CHECK> = Encode::FB_WARN
-
- This is the same as above, except that it warns on error. Handy when
- you are debugging the mode above.
-
- =item perlqq mode (I<CHECK> = Encode::FB_PERLQQ)
-
- =item HTML charref mode (I<CHECK> = Encode::FB_HTMLCREF)
-
- =item XML charref mode (I<CHECK> = Encode::FB_XMLCREF)
-
- For encodings that are implemented by Encode::XS, CHECK ==
- Encode::FB_PERLQQ turns (en|de)code into C<perlqq> fallback mode.
-
- When you decode, C<\xI<HH>> will be inserted for a malformed character,
- where I<HH> is the hex representation of the octet that could not be
- decoded to utf8. And when you encode, C<\x{I<HHHH>}> will be inserted,
- where I<HHHH> is the Unicode ID of the character that cannot be found
- in the character repertoire of the encoding.
-
- HTML/XML character reference modes are about the same, in place of
- C<\x{I<HHHH>}>, HTML uses C<I<NNN>;> where I<NNN> is a decimal number and
- XML uses C<I<HHHH>;> where I<HHHH> is the hexadecimal number.
-
- In Encode 2.10 or later, C<LEAVE_SRC> is also implied.
-
- =item The bitmask
-
- These modes are actually set via a bitmask. Here is how the FB_XX
- constants are laid out. You can import the FB_XX constants via
- C<use Encode qw(:fallbacks)>; you can import the generic bitmask
- constants via C<use Encode qw(:fallback_all)>.
-
- FB_DEFAULT FB_CROAK FB_QUIET FB_WARN FB_PERLQQ
- DIE_ON_ERR 0x0001 X
- WARN_ON_ERR 0x0002 X
- RETURN_ON_ERR 0x0004 X X
- LEAVE_SRC 0x0008 X
- PERLQQ 0x0100 X
- HTMLCREF 0x0200
- XMLCREF 0x0400
-
- =back
-
- =over 2
-
- =item Encode::LEAVE_SRC
-
- If the C<Encode::LEAVE_SRC> bit is not set, but I<CHECK> is, then the second
- argument to C<encode()> or C<decode()> may be assigned to by the functions. If
- you're not interested in this, then bitwise-or the bitmask with it.
-
- =back
-
- =head2 coderef for CHECK
-
- As of Encode 2.12 CHECK can also be a code reference which takes the
- ord value of unmapped caharacter as an argument and returns a string
- that represents the fallback character. For instance,
-
- $ascii = encode("ascii", $utf8, sub{ sprintf "<U+%04X>", shift });
-
- Acts like FB_PERLQQ but E<lt>U+I<XXXX>E<gt> is used instead of
- \x{I<XXXX>}.
-
- =head1 Defining Encodings
-
- To define a new encoding, use:
-
- use Encode qw(define_encoding);
- define_encoding($object, 'canonicalName' [, alias...]);
-
- I<canonicalName> will be associated with I<$object>. The object
- should provide the interface described in L<Encode::Encoding>.
- If more than two arguments are provided then additional
- arguments are taken as aliases for I<$object>.
-
- See L<Encode::Encoding> for more details.
-
- =head1 The UTF8 flag
-
- Before the introduction of Unicode support in perl, The C<eq> operator
- just compared the strings represented by two scalars. Beginning with
- perl 5.8, C<eq> compares two strings with simultaneous consideration of
- I<the UTF8 flag>. To explain why we made it so, I will quote page 402 of
- C<Programming Perl, 3rd ed.>
-
- =over 2
-
- =item Goal #1:
-
- Old byte-oriented programs should not spontaneously break on the old
- byte-oriented data they used to work on.
-
- =item Goal #2:
-
- Old byte-oriented programs should magically start working on the new
- character-oriented data when appropriate.
-
- =item Goal #3:
-
- Programs should run just as fast in the new character-oriented mode
- as in the old byte-oriented mode.
-
- =item Goal #4:
-
- Perl should remain one language, rather than forking into a
- byte-oriented Perl and a character-oriented Perl.
-
- =back
-
- Back when C<Programming Perl, 3rd ed.> was written, not even Perl 5.6.0
- was born and many features documented in the book remained
- unimplemented for a long time. Perl 5.8 corrected this and the introduction
- of the UTF8 flag is one of them. You can think of this perl notion as of a
- byte-oriented mode (UTF8 flag off) and a character-oriented mode (UTF8
- flag on).
-
- Here is how Encode takes care of the UTF8 flag.
-
- =over 2
-
- =item *
-
- When you encode, the resulting UTF8 flag is always off.
-
- =item *
-
- When you decode, the resulting UTF8 flag is on unless you can
- unambiguously represent data. Here is the definition of
- dis-ambiguity.
-
- After C<$utf8 = decode('foo', $octet);>,
-
- When $octet is... The UTF8 flag in $utf8 is
- ---------------------------------------------
- In ASCII only (or EBCDIC only) OFF
- In ISO-8859-1 ON
- In any other Encoding ON
- ---------------------------------------------
-
- As you see, there is one exception, In ASCII. That way you can assume
- Goal #1. And with Encode Goal #2 is assumed but you still have to be
- careful in such cases mentioned in B<CAVEAT> paragraphs.
-
- This UTF8 flag is not visible in perl scripts, exactly for the same
- reason you cannot (or you I<don't have to>) see if a scalar contains a
- string, integer, or floating point number. But you can still peek
- and poke these if you will. See the section below.
-
- =back
-
- =head2 Messing with Perl's Internals
-
- The following API uses parts of Perl's internals in the current
- implementation. As such, they are efficient but may change.
-
- =over 2
-
- =item is_utf8(STRING [, CHECK])
-
- [INTERNAL] Tests whether the UTF8 flag is turned on in the STRING.
- If CHECK is true, also checks the data in STRING for being well-formed
- UTF-8. Returns true if successful, false otherwise.
-
- As of perl 5.8.1, L<utf8> also has utf8::is_utf8().
-
- =item _utf8_on(STRING)
-
- [INTERNAL] Turns on the UTF8 flag in STRING. The data in STRING is
- B<not> checked for being well-formed UTF-8. Do not use unless you
- B<know> that the STRING is well-formed UTF-8. Returns the previous
- state of the UTF8 flag (so please don't treat the return value as
- indicating success or failure), or C<undef> if STRING is not a string.
-
- =item _utf8_off(STRING)
-
- [INTERNAL] Turns off the UTF8 flag in STRING. Do not use frivolously.
- Returns the previous state of the UTF8 flag (so please don't treat the
- return value as indicating success or failure), or C<undef> if STRING is
- not a string.
-
- =back
-
- =head1 UTF-8 vs. utf8 vs. UTF8
-
- ....We now view strings not as sequences of bytes, but as sequences
- of numbers in the range 0 .. 2**32-1 (or in the case of 64-bit
- computers, 0 .. 2**64-1) -- Programming Perl, 3rd ed.
-
- That has been the perl's notion of UTF-8 but official UTF-8 is more
- strict; Its ranges is much narrower (0 .. 10FFFF), some sequences are
- not allowed (i.e. Those used in the surrogate pair, 0xFFFE, et al).
-
- Now that is overruled by Larry Wall himself.
-
- From: Larry Wall <larry@wall.org>
- Date: December 04, 2004 11:51:58 JST
- To: perl-unicode@perl.org
- Subject: Re: Make Encode.pm support the real UTF-8
- Message-Id: <20041204025158.GA28754@wall.org>
-
- On Fri, Dec 03, 2004 at 10:12:12PM +0000, Tim Bunce wrote:
- : I've no problem with 'utf8' being perl's unrestricted uft8 encoding,
- : but "UTF-8" is the name of the standard and should give the
- : corresponding behaviour.
-
- For what it's worth, that's how I've always kept them straight in my
- head.
-
- Also for what it's worth, Perl 6 will mostly default to strict but
- make it easy to switch back to lax.
-
- Larry
-
- Do you copy? As of Perl 5.8.7, B<UTF-8> means strict, official UTF-8
- while B<utf8> means liberal, lax, version thereof. And Encode version
- 2.10 or later thus groks the difference between C<UTF-8> and C"utf8".
-
- encode("utf8", "\x{FFFF_FFFF}", 1); # okay
- encode("UTF-8", "\x{FFFF_FFFF}", 1); # croaks
-
- C<UTF-8> in Encode is actually a canonical name for C<utf-8-strict>.
- Yes, the hyphen between "UTF" and "8" is important. Without it Encode
- goes "liberal"
-
- find_encoding("UTF-8")->name # is 'utf-8-strict'
- find_encoding("utf-8")->name # ditto. names are case insensitive
- find_encoding("utf_8")->name # ditto. "_" are treated as "-"
- find_encoding("UTF8")->name # is 'utf8'.
-
- The UTF8 flag is internally called UTF8, without a hyphen. It indicates
- whether a string is internally encoded as utf8, also without a hypen.
-
- =head1 SEE ALSO
-
- L<Encode::Encoding>,
- L<Encode::Supported>,
- L<Encode::PerlIO>,
- L<encoding>,
- L<perlebcdic>,
- L<perlfunc/open>,
- L<perlunicode>, L<perluniintro>, L<perlunifaq>, L<perlunitut>
- L<utf8>,
- the Perl Unicode Mailing List E<lt>perl-unicode@perl.orgE<gt>
-
- =head1 MAINTAINER
-
- This project was originated by Nick Ing-Simmons and later maintained
- by Dan Kogai E<lt>dankogai@dan.co.jpE<gt>. See AUTHORS for a full
- list of people involved. For any questions, use
- E<lt>perl-unicode@perl.orgE<gt> so we can all share.
-
- While Dan Kogai retains the copyright as a maintainer, the credit
- should go to all those involoved. See AUTHORS for those submitted
- codes.
-
- =head1 COPYRIGHT
-
- Copyright 2002-2006 Dan Kogai E<lt>dankogai@dan.co.jpE<gt>
-
- This library is free software; you can redistribute it and/or modify
- it under the same terms as Perl itself.
-
- =cut
-